Role of grain boundaries in ZnO

Yukio Sato, Yuichi Ikuhara

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

    Abstract

    ZnO is used in a wide variety of applications owing to the electrical properties. Polycrystalline ZnO ceramics have long been used such as varistor, and ZnO films are currently intensively studied for transparent conductor applications. Grain boundary (GB) in ZnO varistor is believed to be the origin of nonlinear current-voltage characteristics, and GB in ZnO films possibly affects the electrical conductivity. It is therefore important to understand the role of ZnO GB on the electrical properties, which should be closely related with the structure in atomic scale. With these viewpoints, we have studied the atomistic structure of ZnO GBs, where the orientation relations of adjacent crystals are well defined. Single GBs studied were obtained by fabricating ZnO bicrystals and the GBs were characterized by scanning transmission electron microscopy (STEM) and theoretical calculations. It is found that coordination number of ions change in ZnO GBs; there are underfold or overfold coordinated ions that are unusual in bulk inside. It is calculated that these atomistic structures alters the electronic structure but would not create deep states in the band gap. On the other hand, when praseodymium (Pr), which is known to be a key dopant element to obtain nonlinear (I-V) characteristics, is added to the GBs, Pr strongly localizes to the GBs and occupies specific atomic sites. Pr facilitates the formation of the acceptorlike defects such as zinc vacancies, which we think that is an important role of Pr on generation of nonlinear (I-V) characteristics. Furthermore, atomic arrangement and localization behavior of Pr are studied for several GBs to obtain fundamental understanding about GB structure formation.

    Original languageEnglish
    Title of host publicationOxide-Based Materials and Devices V
    PublisherSPIE
    ISBN (Print)9780819499004
    DOIs
    Publication statusPublished - 2014
    Event5th Annual Oxide Based Materials and Devices Conference - San Francisco, CA, United States
    Duration: 2014 Feb 22014 Feb 5

    Publication series

    NameProceedings of SPIE - The International Society for Optical Engineering
    Volume8987
    ISSN (Print)0277-786X
    ISSN (Electronic)1996-756X

    Other

    Other5th Annual Oxide Based Materials and Devices Conference
    CountryUnited States
    CitySan Francisco, CA
    Period14/2/214/2/5

    Keywords

    • Double Schottky barrier
    • Electron microscopy
    • Grain boundary
    • Segregation
    • Varistor
    • Zinc oxide

    ASJC Scopus subject areas

    • Electronic, Optical and Magnetic Materials
    • Condensed Matter Physics
    • Computer Science Applications
    • Applied Mathematics
    • Electrical and Electronic Engineering

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